The present invention relates generally to plasma processing of substrates, and more particularly, to methods and systems for plasma processing of a portion of a substrate surface using a small plasma processing chamber.
FIG. 1 is a typical plasma processing chamber 100. The typical plasma processing chamber 100 encloses the entire substrate 102 to be processed. The substrate 102 is loaded into the processing chamber 100. The processing chamber 100 is then sealed and purged to evacuate undesired gases though the outlet 112. A pump 114 may assist in drawing out the undesired gases. Purge gases or processing gases may be pumped into the processing chamber 100 from a processing and/or purging gas source 120 coupled to an input port 122. The purge gases or processing gases may be pumped out the processing chamber 100 to dilute or otherwise remove the undesired gases.
An electrical connection is made to the substrate 102, typically through an electrostatic chuck 104. A plasma signal source 108B is coupled to the substrate 102, typically through the electrostatic chuck 104. A plasma signal source 108A is coupled to an emitter 106 in the processing chamber.
The desired gas(es) at the desired pressures and flowrates are then input to the processing chamber 100. The plasma 110 is initiated by outputting a processing signal (e.g., RF) at the desired frequency and potential from the signal source 108 and imparting the emitted energy to the gases in the processing chamber 100. Ions 110A generated by the plasma directly impinge on the entire surface of the substrate 102. The plasma 110 also generates heat which is absorbed at least in part by the substrate 102. The electrostatic chuck 104 can also cool the substrate 102.
The typical plasma processing chamber 100 is larger than the substrate 100 to be processed so that the entire substrate can be processed within the processing chamber at one time. As the typical plasma processing chamber 100 is increased in size the amount of purging gas and the time required to purge the processing chamber 100 increases. As a result, a larger processing chamber 100 has an increased purging time before and after the substrate 102 is processed.
The throughput of the typical processing chamber 100 is substantially determined by a sum of the substrate loading time, the preprocessing purging time, the substrate processing time, the post-processing purging time and the unloading time. Therefore, the increased purging time of the larger processing chamber 100 decreases the throughput as the size of the substrate 102 increases.
The entire surface of the substrate 102 is processed (e.g., exposed to the plasma 110) at the same time in the typical processing chamber 100. The plasma 110 must be sufficiently large enough to substantially evenly expose the entire surface of the substrate 102 at one time. As the size of the substrate 102 increases the amount of energy required to generate the plasma 110 increases approximately with the square of the area of the surface of the substrate. As a result, the energy requirements for larger substrates 102 increases and the throughput decreases.
In view of the foregoing, there is a need for improved plasma processing systems and methods that is scalable to ever larger substrates without sacrificing throughput.